Ethylene-propylene-diene terpolymer (EPDM) is extensively used in a variety of applications. For example, it is particularly useful as a polymeric sheeting material, which, because of its excellent physical properties, flexibility, weathering resistance, low temperature properties and heat aging resistance, has gained acceptance as a roofing membrane for covering industrial and commercial roofs. These roofing membranes are typically applied to the roof surface in a vulcanized or cured state and serve as an effective barrier to prevent the penetration of moisture to the covered roof.
Traditional EPDM roofing membranes are generally black or very dark in color, and are typically prepared by compounding the base polymer of EPDM with one or more carbon black fillers, processing oil, and other desired ingredients such as plasticizers, antidegradants, adhesive-enhancing promoters, etc., in a suitable mixer, and calendering the resulting compound into the desired thickness. The roofing membrane may also be cured by vulcanizing the resultant sheet in the presence of one or more vulcanizing agents and/or compatible vulcanizing accelerators. Vulcanizing agents such as sulfur or sulfur-donating compounds such as mercaptans are typically used, although vulcanization and curing may be done using other agents or in the presence of other compounds.
While black or dark-colored EPDM membranes have been used for decades as commercial single-ply roofing membranes, such membranes are known to absorb sunlight and become hot. This has led to various environmental and energy concerns. In recent years, great efforts have been made toward producing white and/or other non-black EPDM membranes that are more environmentally friendly and more energy efficient. Various mineral fillers such as clay, talc, silicas, mica, calcium carbonate, and the like, in various combinations, have been added to various roofing membrane formulations to improve energy absorption characteristics.
One particular type of non-black mineral filler that has been used in combination with various clay fillers in non-black EPDM membranes includes silicas. It is known that silica, when used in combination with various clay mineral fillers as an EPDM membrane, can improve certain physical properties such as abrasion resistance and tear resistance. However, silicas, by themselves, do not provide effective reinforcement of the rubber membranes such as carbon black does in black EPDM membranes. Thus, there remains a need for a silica-filled olefinic membrane with improved performance and processing properties beyond those already known.